(1) Field of the Invention
The present invention relates to a flexible coupling for rotating shafts and particularly to a coupling which provides torsional, bending and axial flexibility and more particularly to a flexible coupling that provides two stage torsional flexibility.
(2) Description of the Prior Art
Flexible couplings are useful for connecting two rotating power transmission shafts which must bend or shorten. Many power transfer applications are also vibration and noise sensitive; accordingly, output vibrations or engine vibrations must be isolated from one another. Vibration isolation also reduces the transmission of noise to the outside environment through the drive shaft.
Many prior art universal joints are available which allow the transmission of power through a rotating shaft while allowing the shaft to bend. The most common type of universal joint has a yoke at the end of each shaft. Each yoke is pivotally joined to a web member allowing the shaft freedom of motion in one plane. The yokes are offset from each other at right angles to allow two degrees of freedom. The two yoke universal joint is not axially or torsionally flexible, and the standard universal joint does not provide a great deal of vibration isolation because it allows axial transmission of vibration through the shafts and the webbing.
Elastomeric flexible couplings are also known in the art. In these couplings power is transmitted through an elastomeric member attached between two shafts. The elastomeric member is positioned to allow transverse bending like the two yoke universal joint; however, the elastomeric universal joint also provides flexibility in response to torsional and axial forces, thereby isolating one shaft from vibrations transmitted by the other. A significant problem with elastomeric joints is the tendency of the elastomeric member to fail when subjected to high torque loading, transient vibrations or harsh environmental conditions. Accordingly, elastomeric couplings are used only in low torque, moderate temperature applications.
Selected power transmission machinery requires vibration isolation of the machinery's output shaft from the engine, motor, or other prime mover to prevent noise transmission from the engine to the output shaft environment. In special machinery applications, it is common to use the drive shaft to transmit exhaust gases because of space limitations, and couplings used in these applications should provide for mass transmission from one drive shaft to the other. The isolating member of the machinery should be flexible axially, torsionally and in bending to allow power to be transmitted through the shafting when either the input shaft or output shaft is displaced axially, torsionally or in bending.
Standard elastomeric couplings can provide the required axial and bending flexibility; however, these couplings will not withstand the strain of high torques when increased power transmission is necessary.